The present invention is directed to programmable optical filters and optical circuit arrangements.
Polarization-independent filters that are tunable and/or can simultaneously select a plurality of different wavelengths are required for optical networks having multiple services.
A programmable optical filter is disclosed in a paper by J. B. D. Soole et al, "Monolithic WDM Sources and Detectors for the Long Wavelength Fiber Band Based on an InP Grating Multiplexer/Demultiplexer", Paper OTA2.5, IEEE Lasers and Electro-Optical Society, Annual Meeting Nov. 16-19, 1992, Boston, pp. 690-691. This programmable optical filter is for a plurality of different optical wavelengths and the filter comprises an optical demultiplexer for the spatial separation of the wavelengths from one another and a respective controllable optical amplifier per wavelength for the controlled amplification of the light of this wavelength independent of other wavelengths, wherein the optical amplifiers are in the form of strip-like optical waveguides integrated on a substrate wherein the light waveguide can be optically intensified.
Other known filters having multiple wavelength selection usually function according to the acousto-optical principle. A rapidly-switching, polarization-dependent filter for the selection of a plurality of optical channels from a wavelength comb having channel spacings down to 1 nm is disclosed by S. C. Liew et al, "Applications of the Acousto-Optic Tunable Filter in Local Access Networks", Broadband (FOC/LAN) '90, Baltimore, September 1990, pp. 307-313.
Tunable filters can also be realized with a plurality of arrangements. For example, a thermally tunable polarization-independent filter for the extremely narrow 0.1 nm channel spacing in planar SiO.sub.2 technology is disclosed in an article by N. Takato et al, "128-Channel Polarization-Insensitive Frequency-Selection-Switch Using High-Silica Waveguides on Si", IEEE Photonics Technology Letters, Vol. 2, No. 6, June 1990, pp. 441-443.